More than 270,000 people follow her "Eating NYC" Instagram account. She's considered a social media influencer because her posts theoretically influence her audience about what and where to eat.

Alexa Mehraban gets paid to take pictures of food and post them on Instagram.

CBS News

Gil Eyal is founder of Hypr Brands, which runs a search engine for companies looking for the right influencer to sell their products.

"It's a basic rule of marketing," Eyal said. "The better you target, the more targeted your audience is, the better the outcome is likely to be."

Eyal said this new form of advertising is especially popular in the fashion, beauty and leisure industries. He said there are 10 million influencers, all of whom are supposed to identify paid posts as ads, but as many as 90 percent do not.

"Now, we're seeing a shift towards disclosure because the [Federal Trade Commission] has kind of stamped down and said, 'Okay, we're looking at you,'" Eyal said.

Mehraban has promoted brands as big as Oreo and McDonald's.

"I've kind of had the opportunity to watch this whole cultural transformation unfold," she said.

If a picture is worth a thousand words, for Mehraban, it can also be worth thousands of dollars.

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